linux-kernel - Re: [PATCH V4 3/3] cpufreq: Tegra: implement intermediate frequency callbacks

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Message-ID: <537E285C.6060608@wwwdotorg.org>
Date:	Thu, 22 May 2014 10:39:56 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>, rjw@...ysocki.net
CC:	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, arvind.chauhan@....com,
	swarren@...dia.com, dianders@...omium.org, linux@....linux.org.uk,
	nicolas.pitre@...aro.org, thomas.abraham@...aro.org,
	pdeschrijver@...dia.com
Subject: Re: [PATCH V4 3/3] cpufreq: Tegra: implement intermediate frequency
 callbacks

On 05/21/2014 02:59 AM, Viresh Kumar wrote:
> Tegra had always been switching to intermediate frequency (pll_p_clk) since
> ever. CPUFreq core has better support for handling notifications for these
> frequencies and so we can adapt Tegra's driver to it.
> 
> Also do a WARN() if clk_set_parent() fails while moving back to pll_x as we
> should have atleast restored to earlier frequency on error.

> diff --git a/drivers/cpufreq/tegra-cpufreq.c b/drivers/cpufreq/tegra-cpufreq.c

> @@ -98,10 +96,23 @@ static int tegra_target(struct cpufreq_policy *policy, unsigned int index)
>  	else
>  		clk_set_rate(emc_clk, 100000000);  /* emc 50Mhz */
>  
> -	ret = tegra_cpu_clk_set_rate(rate * 1000);
> +	/* target freq == pll_p */
> +	if (rate * 1000 == clk_get_rate(pll_p_clk)) {
> +		ret = tegra_target_intermediate(policy, index);
> +		goto disable_pll_x;
> +	}

I think the call to tegra_target_intermediate() is wrong here; shouldn't
the cpufreq core guarantee that tegra_target_intermediate() has always
been called before tegra_target(), so there's no need to repeat that
call here?

Also, tegra_target() doesn't seem to follow the rule documented by patch
2/3 that states ->target() should restore the orignal frequency on
error. I'm not even sure if that's possible in general.
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